The present invention relates to a display, particularly, an electrophoretic display in which display is effected by movement of charged particles in a liquid.
As a nonluminescent display, an electrophoretic display has been known which takes advantage of the electrophoretic phenomenon. The electrophoretic phenomenon is the one in which when an external electric field is applied to charged particles in a liquid, the charged particles migrate according to the charge polarity and the direction of the electric filed. As a conventional electrophoretic display, for example, an electrophoretic display has been known in which a colored insulating liquid is used (JP-A-2001-343672). The electrophoretic display disclosed in JP-A-2001-343672 has a structure in which one electrode and the other electrode are opposed to each other with a predetermined separation therebetween, and a liquid is contained in the gap therebetween. When a voltage is applied between the two electrodes, the charged particles are respectively attracted to one of the electrodes according to the charge polarities thereof. In this case, a colored insulating liquid is used so that an observer views either the color of the charged particles or the color of the liquid. Accordingly, an image is displayed by controlling the voltage applied between both electrodes.
As a conventional electrophoretic device in which no colored insulating liquid is used is disclosed, for example, in JP-A-11-202804. In JP-A-11-202804, the device has a structure in which one electrode is small in area and the other electrode is large in area. When a voltage is applied between both electrodes, charged particles are respectively attracted to one of the electrodes according to the charge polarities of the particles. In this case, an observer views the color of the charged particles and the color of either of the electrodes; more specifically, owing to the electrode area difference, the observer mainly views the color of the charged particles when the charged particles are attracted onto the electrode with a large area, while the observer views mainly the color of the electrode when the charged particles are attracted onto the electrode with a small area. Accordingly, by controlling the applied voltage, an image can be displayed.
The insulating liquid in the above described conventional electrophoretic devices is placed the respective compartments separated by partition walls; the partition walls serve to maintain the gap between the upper and lower substrates and limit the migration range of the charged particles respectively within the compartments made up of the partition walls to prevent the diffusion of the charged particles.
In the above described prior art electrophoretic displays, a large number of unit pixels of microspaces formed beforehand by division with the aid of the partition walls are provided with an insulating liquid, and the thus prepared pixels are arranged in a form of matrix to form a two-dimensional display area; however, such a configuration prevents uniform distribution of the insulating liquid over the microspaces, and accordingly it is difficult to achieve a uniform display characteristic over the surface of the display area. An object of the present invention is to provide an electrophoretic display in which the microspaces formed by division into pixels are uniformly provided with an insulating liquid so that a uniform display characteristic is achieved within the display surface.